Currently known well communication systems are either hardwired or wireless systems. Wireless systems are disclosed in U.S. Pat. Nos. 4,893,644 and 5,706,896 and in European patent No. 646304 and have the disadvantage that the acoustic or electromagnetic signals transmitted through the well tubulars and/or fluids passing therethrough can only convey a limited datastream through the well and that the signal to noise level of the transmitted datastreams is low.
Hardwired downhole communication systems are able to transmit large datastreams with a high signal to noise level, but are extremely expensive and difficult to install and/or to modify and maintain after installation, in particular if the well is a multilateral well and the wires need to extend into different well branches.
The system according to the preamble of claim 1 is known from UK patent application GB 2340520. This prior art reference discloses an unbranched well having a horizontal inflow section in which a series of wireless signal transmitters transmit signals in a bucket-brigade mode to a signal receiver at the bottom of the vertical upper part of the well, where the received signal is transmitted via a signal transmission cable.
The known wireless signal transmitters transmit relatively weak acoustic or electromagnetic signals through the produced well fluids, which requires the use of a series of transmitters along the length of the horizontal inflow region of the well. Such an arrangement would be impractical in a multilateral well since the signals transmitted in different well branches would interfere with each other.
The present invention aims to alleviate the disadvantages of the known system and to provide a cost effective and flexible well communication system which is able to transmit large datastreams at a high signal to noise ratio and which can be adapted easily after installation to changing circumstances and to various types of equipment that may be installed during the lifetime of a well, in case the well is a multilateral well and one or more well branches are added after drilling and completion of the original well in which a communication system has already been installed.